Adhesion of butyl rubber to metal



May 3l, 1940 w, Q SMITH @471,905

ADHESION oF BUTYL RUBBER To METAL Filed Feb. l, 1944 mmm-Pol. man

F/Gl-Z Patented May 3l, 1949 ADHESION F BUTYL RUBBER T0 METAL' Winthrope C. Smith, Elizabeth, N. J., assignor to Standard Oil Development Company, a col-,

. poration of Delaware Application February 1, 1944, serial Nn. 520,112

l 1 0 claims. (c1. 154-430) This invention relates to rubber-like structures; relates particularly to rubbery lstructures utilizing the low temperature interpolymers of isoolens and diolens, and relates especially to means -for causing the low temperature polymer to adhere to metal surfaces, other rubbery bodies, and the like.

It has been found possible, by a low temperature polymerization reaction, applied to an olenic mixture containing a major proportion of an isooleiin such as isobutylene with a minor proportion of a diolefln such as butadiene or isoprene, or the like, to produce a highly valuable polymer or copolymer which has some of the physical properties of rubber, and-while it is of relatively very low unsaturation, it is sufiiciently reactive with sulfur in acuring reaction to yield a material having a tensile strength ranging from 500 to 5000 pounds, elongation at break ranging from 500% to 1200%, high flexure resistance,

` high abrasion resistance, high resistance to acid,V

alkali, oxygen, and 'the like, and other valuable and advantageous properties.

However, this polymer material is wholly nonadhesive to metals and to most of the other solid l bodies, and the chemical nature of the polymer material is so greatly diierent from that of natural rubber and the other synthetic rubberlike substances that great difficulty has been encountered in producing unitary structures v composed of metal and adherent polymer, or of polymer adherent to other polymers, resins and rubber-like substances.` It may be noted that the polymer cannot be cyclicized, as is done with natural rubber and it does not form sulfonated products nor hydrochloride products as does natural rubber. l v

It has also been found that various modified forms of natural rubber such as rubber hydrohalide or hydrochloride or cyclicized rubber are A strongly adherent to metals, and to natural rubber and most of the other synthetic rubbers. However, the adhesion between the polymer and modified natural rubber such as Ty Ply S, a

rubber hydrohalide, is so low as to be of little or l no commercial utility. Furthermore, the polymer cannot be mixed with natural rubber and cured satisfactorily because of the very great difference in reactivity with sulfur between the two substances, the rubber curing iirst and taking up all of the sulfur and leaving any admixed polymer wholly uncured,. or, if the rubber is present in small amount, it causes va very troublesome weakening, blistering effect in the polymer which destroys its utility.

Itis now found, however, that polychloroprene, neoprene, can be mixed with the polymer and that such a mixture can be cured into a high strength substance which is strongly adherent to the tie ply material and is also adherent to the polymer per se, thereby permitting of the construction of a strong unitary structure of polymer and metal. In addition, the mixture of polymer and polychloroprene is strongly adherent to a wide range of .other substances 4including natural rubber, the various synthetic rubbers known as Buna, Buna-N and Buna S, prepared from butadiene alone or mixtures oi butadiene with acrylonitrile orstyrene, as well as the other synthetic rubber-like substances and many other synthetic resins.

Thus the process of the invention adheres a low temperature isooleiin-diolefln interpolymer to metal or other substances through the intermediary. of a modified rubber film and an inter,- posed vauxiliary layer containing polychloroprene to yield a strongly adherent, unitary structure;

Other objects and details of the inventionwill lFig. 1 is a sectional view of a rubber and metal v structure utilizing a plural interposed adhering layer, and

Fig. 2 is a sectional view of a structure utilizing natural rubber and a synthetic polymer with an interposed adhering layer.

The copolymer component of the present invention is a low temperature interpolymer of an isoolefln such as isobutylene or 2methy1 butene- 1, or 2-methyl pentane-l, or 2-methyl hexene-l, or the like; with a polyolen such as butadiene,

, or isoprene, or piperylene, or dimethyl butadiene,

or dimethallyl, or myrcene, or the like, substantially any of the polyolefins having from 4 to 12 or 14 carbon atoms per molecule being useful. This material is cooled to a temperature ranging from 20 C. to ,-165 C., the preferred temperature range being from 50C. to 103 C. The cooling may be obtained by the application of a reirigerating jacket to the reactor or by direct admixture of a suitable refrigerant with the oleiinic material. For the reirigerating jacket, practically any of the low boiling liquids, under either pressure or suction, may be used to obtain a desired temperature. For the admixed or internal refrigerant, such substances as liquid propane o r liquid or solid carbon dioxide or liquid ethane or liquid ethylene or even liquid methane `may be used; solid carbon dioxide and liquid` l 3 ethylene being the preferred internal refrigerants.

The oleinic material may consist ofisobutylene in the proportion of from 99.5% to about 1.0% with the diolen in the proportion of l0.5% to 80 or 90%; although the preferred ratio utilizes a major proportion ci the isooleiln and a minor proportion oi the diol.

' The polymerization is conducted by a dissolved Friedel-Crafts catalyst. aluminum chloride in solution in ethyl or methyl chloride or carbon disulde being a preferred catalyst. Alternative- 1y, however, practically any of the Friedel-Crafts catalysts disclosed by N. 0. Calloway -in his article on The Friedel-Crafts Synthesis, printed in the issue of Chemical Reviews, published for the American Chemical Society at Baltimore, in 1935, in volume XVII, No. 3, the article beginning on page 327, the list being particularly well shown on page 375. may be used.

These catalysts may be used as such, or may be modied in various ways such as by the rormation of allroxy compounds or chloro hydroxylates or double salts of two halides or of two metals and two halides, and the like. For the solvent, substantially any of the mono or poly halides having less than 5 or 6 carbon atoms per molecule and freezing points below 0 C., thereby being low-freezing, are useful, since all of them are non-complex-forming with respect to the Friedel-Crafts catalyst.' Alternatively, carbon disulfide and its analogs and homologs may be used, and with the modified Friedel-Crafts catalyst substances various of the lower hydrocarbons such as liquid ethylene, liquid ethane, liquid propane, liquid butane, pentane, hexane, and the like may be used, since these substances also form no complex with the Friedel-Crafts catalyst and all have freezing points below 0 C.

The catalyst may be applied to the cold ble-y nic material in any. desired manner which obtains a rapid dispersal of the catalyst solution into the oleilnic material, a convenient method being the application of the catalyst solution in of water.

The resulting polymer is a solid having a molecular weight ranging between about 25,000 and 250,000 or higher up to about 500,000 (as determined by the Staudinger viscosity method), and an iodine number ranging between about `l and 40 or 50.

The polymer as so prepared is reactive with sulfur in spite of its low iodine number and it is conveniently compounded with such compounding agents as the'various pigments, including carbon black, with zinc oxide, stearic acid, sulfur, and a suliurization aid such as Tuads (tetramethyl thiuram disulilde). f Alternatively,

the sulfur and Tuads may be replaced by` para quinone dioxime or its esters or bythe nitroso compounds such as dinitroso cymene. When so compounded and cured at temperatures ranging from 80 C. to 160 C. for time intervals ransing from a few minutes to several hours, depending upon the curing agent and curing aid, ther '4 material shows tensile strengths ranging from 1000 to 5000 pounds per square inch and elongations at break ranging from 500% to 1.200%.

The second component of the invention is polychloroprene,- which is conveniently obtained commercially under the trade name of neoprene."

This material preferably is an emulsion polymer of chloroprene, CiisCl.

The third component of the invention is a modiiled natural rubber such as the hydrochloride, obtained by .treating natural rubber in solution in such substances as toluene, at low temperatures, with dry hydrogen chloride, or cyclicized rubber such as is obtained .by the treatment of natural rubber in solution in benzol with stannic chloride, or the like, or the rubber sulfonates or other analogous compounds.

The unitary structure of the invention then utilizes a solid body which may be a metal in its various forms, or other solid structure which is coated with a lm of the tie ply; which in turn is covered with a lamina of polychloroprene, either as such or admixed with the low temperature isooleln-diolen interpolymer, and a body of the low temperature interpolymer either as such, or compounded with the various pigments and compounding agents above mentioned. This structure after assembly is then heated to curing temperature for an appropriate length of time to produce the desired integral, cured, unitary structure.

EXAMPLE l A steel structure to which it was desired to adhere the polymer was cleaned of oxide, dirt, and the like, by Sandblasting and was then coated with a lm of the commercial product known as Ty Ply S. This material is a solution in light naphtha of a rubber hydrohalide together with an appropriate amount of accelerator and an appropriate amount of plasticizer and stabilizer. The lm of tie ply was allowed to dry. Simultaneously, test samples were prepared in the form of two, two-inch by six-inch strips of steel which likewise were sand-blasted and coated with the tie ply. The lilms of tie ply on the members were allowed to dry for approximately 30 minutes. A portion of material for the second layer was then prepared according tothe following recipe:

Recipe #1 Parts Neoprene GN (polychloroprene) Phenyl beta naphthyl amine 2 Light calcined magnesia 4 Benzothiazyl disulde 1 Zinc oxide 5 Semi-reinforcing furnace black. 100

This material was prepared on the open roll mill. Simultaneously, a compound of the interpolymer was prepared according-to the following recipe:

Recipe #2 Parts Interpolymer 100 Zinc oxide 5 Stearic acid 3 Sulfur y 1.5l Tetra ymethyl thiuram disulilde 1 semi-reinforcing furnace black.. 100 v--Medium channel black 50 23 parts by weight of the material from Recipe 1 and 23 partsA by weight o! material from Recipe 2 Simultaneously. another portion of compounded interpolymer was prepared according to the following recipe:

Recipe #3 Parts Isobutylene-isoprene interpolymer 100 Zinc oxide 5 Stearic acid 3 Sulfur 2 Tetramethyl thiuram disulfide 1 Semi-reinforcing furnace black 100 Medium channel black .4 50

This material was prepared on the open roll mill and sheeted out into a convenient thickness and a portion rolled down firmly upon the second test strip without interposition of the neoprene-interpolymer compound mixture.

All three structures were "then cured for 30 minutes at a temperature of 311 F. .The steel structure was found to have the 'body of polymer solidly adherent thereto, andto be a sound and satisfactory unitary structure.

To determine the strength of this structure, the first testy sample was pulled upon the Scott tester and a strength of `56 pounds per linear inch was `found. Thereafter the second test sample, prepared without the interposed neoprene compound-interpolymer compound, was pulled and found to have astrength of only 21 pounds per linear inch. Both samples were tested on the Scott tester by pulling the cured compound away from the metal at a rate of 2 inches per minute.

.EXAMPLE 2 An analogous structure was prepared utilizing anatural rubber element as the base member rather than a metal structure. In preparing this structure, the natural rubber vwas compounded according to the following recipe:

.Recipe #4 Parts .by 'weight Smoked sheets 100 Zinc oxide -a 5 Stearic acid 3 Sulfur 1 1.5 Mercaptobenzothiazole s 0.5 Semi-reinforcing furnace black '75 This material was formed into the desired shape; then the surface was butfed and freshened with naphtha to soften it and it was then given a coat of the Ty Ply S solution, as in Example 1. The Ty Ply S coating was allowed to dry for 30 min utes. Then t'he coating of Ty Ply S was given *two coats of the interpolymer solution prepared from Recipe #l and Recipe #2, as in Example. 1, each coat being allowed to dry for 30 minutes. A portion of material compounded accordingto Recipe #2 was then sheeted out and the sheeted out material was then rolled firmly down onto the third coat. Additional quantities of the material from Recipe #2 were then applied to the surface to prepare the material in the desired shape. The

whole assembly was then cured at an appropriate temperature for a proper time. to produce a unitary structure, a portion of which consisted of natural rubber and a further portion of which consisted of the low temperature interpolymer, with a veryfirm bond between the two. Upon determination of tensile strength, the .tensile strength of the composite laminar assembly was found to be nearly equal to the tensile strength of the cured interpolymer, and the assembled structure broke at random at various points in the structure, apparently determined entirely by chance. This example shows the ease with which a strongly adherent unitary structure consisting of laminae of natural rubber and the interpolymer of isobutylene with a dioleiin may be prepared.

In the above example, the natural rubber was assembled in uncured condition and the whole structure was cured at once. This, however, is not necessary, since the natural rubber may be separately cured, either fully cured, or given a part cure or set cure, as desired. In the event that the natural rubber is partly or entirely cured, it

is desirable that this shall be done with a minli mum of accelerator, in order that the final curing of the polymer may not overcure the natural rubber.

EXAMPLE 3 A similar -structure to Examples 1 and 2 was prepared, utilizing for the base member a portion of the emulsion interpolymer of butadiene with styrene known commercially as Buna S." This material was preferably compounded with sulfur, an accelerator, carbon black, zinc oxide and stearic acid in the usual manner, according to the following compounding recipe #5.

Recipe #5 Buna S 100 Zinc oxide 5 Stearic acid 1 Sulfur 2 Benzothiazyldisulilde 0.75 Semi-reinforcing furnace black The compounded material, preferably uncured, was then formed into the desired shape, and the desired surface was freshened with naphtha or by buiing', as in Example 2. The freshened surface was thenv given a coating of the Ty Ply S, as in Example 1, and the coating was allowed to dry for `approximately 30 minutes. Over the Ty Ply coating there were then applied two coat.- ings prepared from Recipes 1 and 2, as in Example 1, each coat also being allowed to dry for approximately 30 minutes. A portion lof the low temperature interpolymer of isobutylene with a v pared without curing and the unitary structure is.

` cured as a whole, the amount of curing time and accelerator in the several layers 'being adjusted so that all are cured to the optimum degree in The material was then with their respective curing agents present therein into a coherent unitary body.

4. In a process for adhering a cured layer ci isooleiin-dioleiinpolymer to a metal base, the

ply .and the neoprene-containing lamina. The invention is not however limited to structures utilizingmetalas a foundation.' The interposed laminae of neoprene and Ty lPlyS4 are also useful in producing unitary structures of the isooleiin-dioleiin polymer withwsuch substances as natural rubber, or the various Bunas, or neoprene improvement which comprises coating the metal base with a layer of halogenated rubber that adheres to the metal'base; applying over the layer of halogenated rubber a layer oipoiychlcrcprene mixed with isooien-.diolefin interpolymer; applying over said layer an isoolen-diolefin polymer; and simultaneously curing the halogenated rubber, the polychloroprene, and the interpolymers in said layers with their respective curing agents into a unitary structure with the metal base. v

5. In a process as described in claim e, said isooleiin-dioleiln inter-polymer being an interitseli, or various of the synthetic and natural resins such as Bakelite, the methacrylate resins, shellac, gum damar, copai, and the like, either as such or when illleds-withpigments or other ullers such as ...wood hour. ground cork, cotton linters, fabric, and the Iilse.- vlier this purpose various other tie ply substances may be used such as .Vulcaloch? which is cyclicized rubber, or Bostic which appears to be a rubber sulfonate, or the like, may also be used.

Thus 'the invention produces a unitary structure, one member of which is a low-temperature interpolymer oi an isoolefln with a diolen which is adherent through the agency of a polychloroprene containing lamina to another solid body.

While there are above disclosed but a limited number of embodiments of the process and product of the invention, it is possible to produce still other embodiments without departing from the inventive concept herein disclosed and it is therefore desired that only such limitations be imposed on the appended claims as are stated therein.

The invention claimed is:

l. In a process for adhering an isoolen-diolen iin interpolymer to a solid body, the improvement Whichcomprises interposing between said interpolylner and the solid body a dual laminae, one thereof comprising polychloroprene mixed with isoolen-diolen interpolymer and the other thereof comprising a lm oi modified rubber adherent to the said solid body and the lamina which comprises covering the metal base with a nlm of halogenated rubber cement, drying said nlm kby evaporating solvent therefrom, coating the dried iilm of said cement with asolution coating comprising polychloroprene and isoolen-dioleiin interpolymer in a solvent, drying said coating, coveringthe dried coating with a sheet of isooleiln-diolen interpolymer, and curing the halogenated rubber, polychloroprene, and the interpolymer in the nlm coating and sheet respectively polymer containing a maior proportion of isobutylene and a minor proportion of isoprene,

6. A unitary structure comprising a solid base, a cured ilm of modified rubber adherent thereto, a lamina comprising e curedmixture of polychloroprene with isoolefln-diolefin interpolymer adherent to said film, and a vsheet of cured'isooleniin-diolen interpolymer integrally adherent vto the lamina.

'7. A unitary structure comprising a metal base, a nlm of cured halogenated rubber adherent to said base, a lamina comprising a cured mixture ci polychloroprene with an isobutylene-isoprene inter-polymer adherent to said lm, and a layer of cured isobutylene-isoprene interpolymer ad- 50 Number herent to said lamina.

8. A unitary structure comprising a natural rubber base, a nlm ofcured halogenated rubber adherent to said base, a lamina comprising a cured mixture of polychloroprene with an isooleiin-diolen interpolymer adherent to said film, and e. cured layer of isooleiln-dioleiin interpolymer adherent to said lamina.

9. A unitary structure comprising a synthetic l REFERENCES CITED The following references are of record in the ille of this patent: f

UNITED STATES PATENTS Name Date Thomas Feb. 16, 1943 y Juve July 4, 1944 FOREIGN PATENT$ Country Date Great Britain Mar. 10, 1938 OTHER REFERENCES Number Morris Jan. 2, 1945 

